In recent years, solid-state light illuminators, such as LASERs and light-emitting-diodes (LEDs), and other narrow-banded light illuminators capable of producing phase-coherent light, such as wavelength specific plasma lamps, have drawn significant attention as alternative light sources to traditional light sources, such as arc lamps, for use in imaging systems, especially imaging systems employing light valves each comprising an array of individually addressable pixels, due to many advantages, such as compact size, greater durability, longer operating life, and lower power consumption.
Regardless of the widely embraced superior properties of solid-state illuminators over traditional light sources, it is however difficult to optically couple solid-state illuminators with light valves. For example, it is difficult to generate a far-field illumination area with uniform illumination intensity at the light valve location using solid-state or narrow-banded light illuminators because the illumination light from the solid-state illuminators and most narrow-banded illuminators are highly collimated as compared to the light from traditional illuminators.
Therefore, it is desired to have an optical device and/or an optical architecture, with which light of different colors from the illuminators can be incident to the target (e.g. light valve) simultaneously; and narrow-banded light (e.g. lasers) can be efficiently coupled to the target.